1. Field of the Invention
This patent relates to manually operated electrical switches. More particularly, this patent relates to a manually operated electrical switch that uses a shaft with a plurality of cams operatively connected to electrical contacts to provide the required switching action for rerouting electrical power either through or around AC variable frequency inverter drives.
2. Description of the Related Art
Inverter drives, or inverters for short, are solid state devices used to vary the speed of common three phase electric motors. Inverters are common in industry and are used in conveyors, fans, cooling towers, extruders, and other applications. However, since inverters are solid state devices, they are vulnerable to lightning strikes, power surges, low voltages, and other disturbances in the electrical line. When disturbances occur, inverter drives can fail. Failure of the inverter drive can stop the motor from operating, thus stopping the application.
Several methods have been developed to isolate inverters during electrical disturbances. However, these methods involve expensive and unreliable contactors, relays and timers.
The present invention is designed to provide a simple means of isolating an inverter drive during an electrical disturbance to allow a motor to continue at full speed/full power operation until a safe stopping point is reached. This is accomplished by providing an inverter bypass safety switch that can route electrical power through or around an inverter simply by turning a handle on the switch.
Thus it is an object of my invention to provide a simple and reliable means for isolating an inverter during electrical disturbances so that the motor can continue at full speed/full power operation until a safe stopping point is reached.
Another object of the present invention is to provide a mechanical means for isolating an inverter. The present invention does not require contactors, relays, solenoids, or coils that can consume power, stick, or burn out.
Still another object of the present invention is to provide a means for isolating an inverter that uses positive break contacts. Should a contact “weld”, the switch handle cannot be turned. If the switch handle cannot be turned, the contacts cannot transfer. If the switch handle is able to be turned, the contacts transfer. This feature assures the operator that when the switch has been turned the contacts have been transferred.
Yet another object of the present invention is to provide a switch having positive removal of the electrical power from the inverter drive. In other words, the switch can be used to disconnect power from both the incoming lines into the inverter and outgoing lines from the inverter.
Further and additional objects will become apparent from the description, accompanying drawings, and appended claims.
While other less desirable methods have been developed to isolate inverters during electrical disturbances, no prior inverter bypass switch is known that embodies and possesses all the aforementioned characteristics.